after using my Epson 3800 for some years, I would like to buy a new 3880.

Now, what to do with my current 3800 (compatible) ink cartridges containing still a lot of ink?

After unpacking the 3880, can I use the old (compatible) 3800 inks instead of the new ink cartridges supplied with the printer? And if the old cartridges go empty, then use the new supplied cartridges.

Are there any drawbacks or issues with this approach? Or what is the best approach to avoid wasting the ink of the 3800 cartridges?

You can use the old inks from the 3800 except for the magenta's. That being said, you should use the ink that comes with the 3880 and when you need to replace an empty cartridge you can use the 3800's as long as they are not either of the magenta's. The 3800 and 3880 have the same ink codes except for the magenta's.

You can use Epson 3800 ink in the 3880. The only 3800 colors you can't use in the 3880 is the magenta and light magenta. The 3880 replaces those with the Vivid Magenta and Vivid Light Magenta. The other colors can be used in either printer. Go to B&H and check out Epson K3 ink carts. The same non-vivid color inks are sold for both the 3800 and 3880.

My main concern was not about the compatibility of the cartridges, but about the sequence when to use which cartridges (firstly new cartridges, then used cartridges OR firstly used cartridges then new cartridges).

- First approach would be: unpack the 3880, insert the new cartridges supplied with the 3880. But until some new cartridges go empty, what should I do with my old 3800 cartridges? Can I remove them from the 3800? Or should I keep them in the 3800? How can I avoid that the ink is drying?

- Second approach would be: unpack the 3880, insert the used/old 3800 cartridges, insert the new 2 vivid ink cartridges (supplied with the 3880). Will this cause some issues because the new 3880 is initially used with used/old 3800 cartridges?

I would mover the 3800 ink to the 3880 and leave the 3880 ink in their sealed packages until the original 3800 ink runs out. Why would you want to open up sealed ink and put your used 3800 ink into zip locked bags?

You can use all the 3800 inks in the 3880 but you will not get all the benefits of the new magenta until you switch to them. I have been using the older set ( although it was the Lyson brand in my 2880. Once my supply of old magenta was used up I would switch to the new support,you. Might have to modify my profiles. Not a big deal.

If you are using the 3800 carts to prime the 3880 ( which you can do except for the magenta) be sure they are at least 1/3 full, because of the ink level gets too low in a cart during the prime, the prime will fail, and when you rerun it, it will use the same amount of ink as a full prime, resulting in tha waste of a lot of ink.